The aim of the program is to determine the mechanisms by which laser phototherapy is effected in the treatment of cardiovascular disease. This research is focused on the effect of laser light on those tissues involved in the following cardiovascular disorders: 1. atherosclerotic coronary arterial narrowing 2. calcific aortic stenosis 3. hypertrophic cardiomyopathy (IHSS) Ultimately, one would anticipate being able to improve the treatment of these disorders by means of laser phototherapy. In some cases, the unique features of laser technology might reasonably be expected to result in development of a trans-arterial catheter-guided fiberoptic system that would allow a percutaneous approach to replace contemporary approaches that presently require thoracotomy. In such an approach the appropriate laser light--appropriate in terms of wavelength, power and exposure time--is directed to the tissue site by an optical fiber for photoeradication of the pathologic lesion. In order to accomplish this ultimate aim, this proposal is designed to deal with the fundamental fact that each specific cardiovascular problem requires a specific laser wavelength and power combination. The appropriate combination of wavelength and power is a function of absorbance, scattering, heat transport and photoreactivity of the tissue region illuminated. The defining of such mechanisms of laser action for the cardiovascular conditions listed above is the aim of the present proposed research program. Using state-of-the-art laser systems and fiberoptics technology, we shall attempt to (1) define the optimum laser conditions for cardiovascular phototherapy, and (2) test these conditions in simulated clinical usage, employing a catheter-fiberoptic system in animal models.